<script>
	var num;
	var a = parseInt(prompt("请输入第一个数："));
	var b = parseInt(prompt("请输入第二个数："));
	var c = prompt("请输入运算符号：");
	switch(c) {
		case "+":
		num = a + b;
			break;
		case "-":
			num = a - b;
			break;
		case "*":
		num = a * b;
		break;
	        case "/":
		num = a / b;
		break;
		default:
		alert("输入运算符有误！");
		break;
			}
      alert("两数的运算结果是：" + a + c + b+ "=" + num);
		</script>